Various orthopedic surgical procedures require access to the cancellous bone within vertebrae. Examples include vertebroplasty and kyphoplasty. Typically such procedures create such access by conventional steps of drilling an access hole through the vertebral wall, advancing the drill distally further into the cancellous bone itself, followed by withdrawal of the drill. The void so created in the cancellous bone is known as a drill channel for purposes of this application.
Subsequent surgical treatment of the vertebrae may require additional removal, compaction, tamping, or (in general) addressing in some manner the remaining cancellous bone within the vertebrae that surrounds the drill channel. A working cannula is typically inserted into the drilled hole in the vertebral wall to access the remainder of the drill channel with various tools and components that may be distally advanced into the vertebrae through the lumen of the cannula, and proximally withdrawn from the lumen when desired. The fixed inner diameter of the lumen places significant restraints on the dimensions of such tools and components.